Wavelength division multiplexing with parallel arrayed signal paths for increased channel density

ABSTRACT

Disclosed herein is wavelength-division multiplexing (WDM) and demultiplexing with signal entry and exit in a common routing surface to increase channel density. In particular, disclosed is a WDM assembly including a plurality of common ports and a plurality of channel sets having one or more channel ports. The WDM assembly includes a first routing surface with a first WDM passband and a second routing surface offset from the first routing surface. The second routing surface is configured to reflect at least one signal passed through the first routing surface back through the first routing surface at a laterally different location. Optical signal paths of at least a portion of the common ports are parallel to and offset from one another. In certain embodiments, such a configuration may increase channel density and decrease a form factor (e.g., footprint).

PRIORITY APPLICATION

This application claims the benefit of priority of U.S. ProvisionalApplication No. 63/057,566, filed on Jul. 28, 2020, the content of whichis relied upon and incorporated herein by reference in its entirety.

BACKGROUND

The disclosure relates to wavelength-division multiplexing (WDM) anddemultiplexing, and more particularly, to WDM assemblies with parallelarrayed signal paths for increased channel density.

Wavelength-division multiplexing (WDM) is a technology that multiplexes(e.g., adds) a number of distinct wavelengths of light onto a singleoptical fiber and demultiplexes (e.g., divides) a number of distinctwavelengths of light from a single optical fiber, thereby increasinginformation capacity and enabling bi-directional flow of signals.Multiple optical signals are multiplexed with different wavelengths oflight combined by a multiplexer at a transmitter, directed to a singlefiber for transmission of the signal, and split by a demultiplexer todesignated channels at a receiver. By combining multiple channels oflight into a single channel, WDM assemblies and associated devices canbe used as components in an optical network, such as a passive opticalnetwork (PON).

There is an increasing need for faster transceivers, and accordingly,transceivers with more channels (as electronic signal speed cannotincrease unlimitedly). Digital signal processing (DSP) and other signalmodulation techniques (e.g., 4-level pulse amplitude modulation (PAM4))may be used to increase the data transfer rate but are extremely costly,especially compared to passive techniques. Such passive techniquesinclude arrayed waveguide grating (AWG) planar lightwave circuit (PLC)and optical thin film filter (TFF) free space wavelength divisionmultiplexing (WDM). Although AWG PLC may be more compact, TFF WDM issuperior in loss, passband ripple, passband width, isolation, andthermal stability.

As an example, FIG. 1 is a diagram illustrating a WDM assembly 100including a single WDM common port 102 in optical communication with aset 104 of four WDM channel ports 106(1)-106(4) by a plurality of WDMfilters 108(1)-108(4) and reflective surfaces 110(1)-110(3). The WDMfilters 108(1)-108(4) and the reflective surfaces 110(1)-110(3) arearranged to form an optical path 112 between the common port 102 andeach of the channel ports 106(1)-106(4). In particular, each of the WDMfilters 108(1)-108(4) has a TFF with a unique passband to allow aportion of the optical signal to pass through the WDM filters108(1)-108(4) and to reflect the remaining portion of the optical signaltowards the reflective surfaces 110(1)-110(3), which in turn reflect theremaining portion of the optical signal towards another one of theremaining WDM filters 108(2)-108(4).

The total data transfer rate can be increased by increasing the numberof wavelength channels of an optical transceiver, but there is a growingdemand to decrease dimensions of the optical transceiver, therebyresulting in significant decreases in the pitch P1-P3 between adjacentchannels. However, there are restrictions on decreasing the size of theWDM filters 108(1)-108(4) and/or reflective surfaces 110(1)-110(3). Forexample, there is a minimum surface area required for proper signalperformance (e.g., signals may be negatively affected if too close to anedge of the TFF of a WDM filter 108(1)-108(4) and/or reflective surface110(1)-110(3)). Further, there is a minimum surface area to apply a TFFto a substrate of a WDM filter 108(1)-108(4) (e.g., 500 microns in alateral dimension). In other words, there are performance andmanufacturing limitations on decreasing the sizes of the WDM filters108(1)-108(4) and/or reflective surfaces 110(1)-110(3), but there is aneed to decrease the pitch P1-P3 between adjacent channels and increasechannel density.

SUMMARY

One embodiment of the disclosure relates to a wavelength-divisionmultiplexing (WDM) assembly. The WDM assembly includes a first commonport configured for optical communication of a first multiplexed signalincluding a first signal component and a second signal component. TheWDM assembly further includes a first channel set including a firstchannel port configured for optical communication of the first signalcomponent of the first multiplexed signal, and a second channel portconfigured for optical communication of the second signal component ofthe first multiplexed signal. The WDM assembly further includes a secondcommon port configured for optical communication of a second multiplexedsignal comprising a first signal component and a second signalcomponent. The WDM assembly further includes a second channel setincluding a first channel port configured for optical communication ofthe first signal component of the second multiplexed signal, and asecond channel port configured for optical communication of the secondsignal component of the second multiplexed signal. The WDM assemblyfurther includes at least one first routing surface having a firstpassband, the at least one first routing surface being configured toreflect the first signal component of the first multiplexed signal andthe first signal component of the second multiplexed signal, and passthe second signal component of the first multiplexed signal and thesecond signal component of the second multiplexed signal. The WDMassembly further includes at least one second routing surface configuredto reflect the second signal component of the first multiplexed signaland the second signal component of the second multiplexed signal backthrough the at least one first routing surface. The first common port,the at least one first routing surface, the at least one second routingsurface, and the second channel port of the first channel set areconfigured to define a first optical signal path in a first signalplane. The second common port, the at least one first routing surface,the at least one second routing surface, and the second channel port ofthe second channel set are configured to define a second optical signalpath in a second signal plane parallel to and offset from the firstsignal plane. The at least one first routing surface is positioned inthe first optical signal path between the first common port and the atleast one second routing surface, and between the at least one secondrouting surface and the second channel port of the first channel set.The at least one first routing surface is positioned in the secondoptical signal path between the second common port and the at least onesecond routing surface, and between the at least one second routingsurface and the second channel port of the second channel set.

An additional embodiment of the disclosure relates to awavelength-division multiplexing (WDM) assembly. The WDM assemblyincludes a housing. The WDM assembly further includes a first commoncollimator positioned within the housing and configured for opticalcommunication of a first multiplexed signal, the first multiplexedsignal including a first signal component and a second signal component.The WDM assembly further includes a first common fiber optic pigtailcoupled to the first common collimator and extending from the housing.The WDM assembly further includes a first channel set including a firstchannel collimator positioned within the housing and configured foroptical communication of the first signal component of the firstmultiplexed signal, a first channel fiber optic pigtail operativelycoupled to the first channel collimator of the first channel set andextending from the housing, a second channel collimator positionedwithin the housing and configured for optical communication of thesecond signal component of the first multiplexed signal, and a secondchannel fiber optic pigtail operatively coupled to the second channelcollimator of the first channel set and extending from the housing. TheWDM assembly further includes a second common collimator positionedwithin the housing and configured for optical communication of a secondmultiplexed signal, the second multiplexed signal comprising a firstsignal component and a second signal component. The WDM assembly furtherincludes a second common fiber optic pigtail coupled to the secondcommon collimator and extending from the housing. The WDM assemblyfurther includes a second channel set including a first channelcollimator positioned within the housing and configured for opticalcommunication of the first signal component of the second multiplexedsignal, a first channel fiber optic pigtail operatively coupled to thefirst channel collimator of the second channel set and extending fromthe housing, a second channel collimator positioned within the housingand configured for optical communication of the second signal componentof the second multiplexed signal, and a second channel fiber opticpigtail operatively coupled to the second channel collimator of thesecond channel set and extending from the housing. The WDM assemblyfurther includes at least one first routing surface having a firstpassband. The at least one first routing surface is configured toreflect the first signal component of the first multiplexed signal andthe first signal component of the second multiplexed signal, and passthe second signal component of the first multiplexed signal and thesecond signal component of the second multiplexed signal. The WDMassembly further includes at least one second routing surface configuredto reflect the second signal component of the first multiplexed signaland the second signal component of the second multiplexed signal backthrough the at least one first routing surface. The first commoncollimator, the at least one first routing surface, the at least onesecond routing surface, and the second channel collimator of the firstchannel set are configured to define a first optical signal path in afirst signal plane. The second common collimator, the at least one firstrouting surface, the at least one second routing surface, and the secondchannel collimator of the second channel set are configured to define asecond optical signal path in a second signal plane parallel to andoffset from the first signal plane. The at least one first routingsurface is positioned in the first optical signal path between the firstcommon collimator and the at least one second routing surface, andbetween the at least one second routing surface and the second channelcollimator of the first channel set. The at least one first routingsurface is positioned in the second optical signal path between thesecond common collimator and the at least one second routing surface,and between the at least one second routing surface and the secondchannel collimator of the second channel set.

An additional embodiment of the disclosure relates to a method of usinga wavelength-division multiplexing (WDM) assembly. The method includesrouting, along a first optical signal path in a first signal plane, afirst multiplexed signal from a first common port to a first channelset. The routing of the first multiplexed signal includes propagating,from a first common port, the first multiplexed signal including a firstsignal component and a second signal component. The routing of the firstmultiplexed signal further includes reflecting the first signalcomponent of the first multiplexed signal off at least one first routingsurface having a first passband to a first channel port of a firstchannel set. The routing of the first multiplexed signal furtherincludes passing the second signal component of the first multiplexedsignal through the at least one first routing surface. The routing ofthe first multiplexed signal further includes reflecting, off at leastone second routing surface, the second signal component of the firstmultiplexed signal passed through the at least one first routingsurface. The routing of the first multiplexed signal further includespassing the second signal component of the first multiplexed signalreflected from the at least one second routing surface through the atleast one first routing surface to a second channel port of the firstchannel set. The method further includes routing, along a second opticalsignal path in a second signal plane parallel to and offset from thefirst signal plane, a second multiplexed signal from a second commonport to a second channel set. The routing of the second multiplexedsignal includes propagating, from a second common port, a secondmultiplexed signal comprising a first signal component and a secondsignal component. The routing of the second multiplexed signal furtherincludes reflecting the first signal component of the second multiplexedsignal off the at least one first routing surface having the firstpassband to a first channel port of a second channel set. The routing ofthe second multiplexed signal further includes passing the second signalcomponent of the second multiplexed signal through the at least onefirst routing surface. The routing of the second multiplexed signalfurther includes reflecting, off the at least one second routingsurface, the second signal component of the second multiplexed signalpassed through the at least one first routing surface. The routing ofthe second multiplexed signal further includes passing the second signalcomponent of the second multiplexed signal reflected from the at leastone second routing surface through the at least one first routingsurface to a second channel port of the second channel set.

Additional features and advantages will be set out in the detaileddescription which follows, and in part will be readily apparent to thoseskilled in the art from that description or recognized by practicing theembodiments as described herein, including the detailed descriptionwhich follows, the claims, as well as the appended drawings.

It is to be understood that both the foregoing general description andthe following detailed description are merely exemplary, and areintended to provide an overview or framework to understanding the natureand character of the claims. The accompanying drawings are included toprovide a further understanding, and are incorporated in and constitutea part of this specification. The drawings illustrate one or moreembodiment(s), and together with the description serve to explainprinciples and operation of the various embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram of a wavelength-divisional multiplexing (WDM)optical assembly including a single WDM common port in opticalcommunication with four WDM channel ports via four WDM filters;

FIG. 2A is a diagram of a WDM assembly of the present disclosureincluding a first routing surface and a second routing surface offsettherefrom to have a signal enter and exit in the same first routingsurface in a laterally different location;

FIG. 2B is a top view of the WDM assembly of FIG. 2A with a differentoffset and corresponding different pitch between adjacent channel paths;

FIG. 3A is a top view of another embodiment of the WDM assembly of FIGS.2A-2B including a WDM filter with the first routing surface and thesecond routing surface opposite thereto;

FIG. 3B is a top view of another embodiment of a WDM assembly includingthe WDM filter of FIG. 3A;

FIG. 4A is a top view of another embodiment of the WDM assembly of FIGS.2A-2B including the first routing surface at a back of a first WDMfilter and the second routing surface at a back of a second WDM filter;

FIG. 4B is a top view of the WDM filters of FIG. 4A illustratingconstant signal pitch with a different thickness of the first WDMfilter;

FIG. 4C is a top view of the WDM filters of FIG. 4A illustrating adifferent signal pitch with a different thickness of the second WDMfilter;

FIG. 4D is a top view of another embodiment of the WDM assemblyincluding the WDM filters of FIGS. 4A-4C;

FIG. 4E is a top view of another embodiment of the WDM assembly of FIG.4D;

FIG. 5 is a top view of another embodiment of the WDM assembly of FIGS.2A-2B with the first routing surface at a front of a first WDM filterand the second routing surface at a front of a mirror;

FIG. 6A is a top view of another embodiment of the WDM assembly of FIGS.2A-2B with the first routing surface at a back of a first WDM filter andthe second routing surface at a front of a routing component and offsetfrom the back of the first WDM filter;

FIG. 6B is a top view of another embodiment of the WDM assembly of FIG.6A with the first routing surface at a back of a first WDM filter and aplurality of second routing surfaces at a front of a plurality ofrouting components and offset from the back of the first WDM filter;

FIG. 7 is a top view of another embodiment of the WDM assembly of FIGS.2A-6B with routing surfaces in a stacked orientation for routing fourmultiplexed signals from four common ports to four channel sets,respectively;

FIGS. 8A and 8B are top views of another embodiment of the WDM assemblyof FIGS. 2A-6B with routing surfaces in a cascaded orientation forrouting four multiplexed signals from four common ports to four channelsets, respectively;

FIG. 9A is a perspective view of another embodiment of the WDM assemblyof FIGS. 2A-7 routing parallel and offset signal paths;

FIG. 9B is a front view of the WDM assembly of FIG. 9A;

FIG. 9C is a side view of the WDM assembly of FIG. 9A;

FIG. 10 is a perspective view of another embodiment of the WDM assemblyof FIGS. 2A-7 with a plurality of WDM filter stacks, each routing one ofa plurality of parallel and offset signal paths;

FIG. 11A is a bottom view of a bottom surface of a WDM filter stackillustrating a planar configuration of common ports and signal paths ofthe WDM assembly of FIG. 7;

FIG. 11B is a bottom view of a bottom surface of a WDM filter stackillustrating a parallel configuration of common ports and signal pathsof the WDM assembly of FIGS. 9A-9C;

FIG. 11C is a bottom view of a bottom surface of a WDM filter stackillustrating a grid array of common ports and signal paths combiningfeatures of the WDM assembly of FIGS. 7 and 9A-9C;

FIG. 12 is a perspective view of another embodiment of the WDM assemblyof FIGS. 2A-6B and FIGS. 8A-8B routing parallel and offset signal pathsin a cascaded orientation;

FIG. 13A is a flowchart of steps for using any of the WDM assemblies ofFIGS. 2A-12;

FIG. 13B is a flowchart of steps for using any of the WDM assemblies ofFIGS. 7-12;

FIG. 14 is a top view of an example micro-optical device used with anyof the components and assemblies of FIGS. 2A-12;

FIG. 15 is a perspective view of an example steel-tube collimator foruse with the components and assemblies of FIGS. 2A-12;

FIG. 16A is a perspective view of an example square tube collimator foruse with the components and assemblies of FIGS. 2A-12;

FIG. 16B is a cross-sectional top view of the square tube collimator ofFIG. 16A;

FIG. 17A is a side view of an example compact collimator for use withthe components and assemblies of FIGS. 2A-12;

FIG. 17B is a close-up side view of the compact collimator of FIG. 17A;

FIG. 18A is a perspective view of an example array of the compactcollimators of FIGS. 17A-17B;

FIG. 18B is a close-up front view of the array of compact collimators ofFIG. 18A;

FIG. 19 is a perspective view of an example of a fiber array unit (FAU)for use with the components and assemblies of FIGS. 2A-12; and

FIG. 20 is a perspective view of a WDM device including the WDM assemblyof FIGS. 7-12.

DETAILED DESCRIPTION

Reference will now be made in detail to the present preferredembodiments, examples of which are illustrated in the accompanyingdrawings. Whenever possible, the same reference numerals will be usedthroughout the drawings to refer to the same or like parts.

The embodiments set out below represent the information to enable thoseskilled in the art to practice the embodiments. Upon reading thefollowing description in light of the accompanying drawing figures,those skilled in the art will understand the concepts of the disclosureand will recognize applications of these concepts not particularlyaddressed herein. It should be understood that these concepts andapplications fall within the scope of the disclosure and theaccompanying claims.

Reference Numbers and Terminology

The use herein of ordinals in conjunction with an element is solely fordistinguishing what might otherwise be similar or identical labels, suchas “first layer” and “second layer,” and does not imply a priority, atype, an importance, or other attribute, unless otherwise stated herein.

The term “about” used herein in conjunction with a numeric value meansany value that is within a range of ten percent greater than or tenpercent less than the numeric value.

As used herein, the articles “a” and “an” in reference to an elementrefers to “one or more” of the element unless otherwise explicitlyspecified. The word “or” as used herein is inclusive unless contextuallyimpossible. As an example, the recitation of A or B means A, or B, orboth A and B.

The phrase “surface” as used herein refers to an outermost portion of anitem, and includes a thickness of the outermost portion of the item. Theprecise thickness is generally not relevant to the embodiments, unlessotherwise discussed herein. For example, a layer of material has asurface which includes the outermost portion of the layer of material aswell as some depth into the layer of material, and the depth may berelatively shallow, or may extend substantially into the layer ofmaterial. The sub-wavelength openings discussed herein are formed in asurface, but whether the depth of the sub-wavelength openings extendspast the depth of the surface is generally not relevant to theembodiments.

It will be understood that when an element is referred to as being“connected” or “coupled” to another element, it can be directlyconnected or coupled to the other element or intervening elements may bepresent. In contrast, when an element is referred to as being “directlyconnected” or “directly coupled” to another element, there are nointervening elements present.

The use herein of “proximate” means at, next to, or near.

The terms “left,” “right,” “top,” “bottom,” “front,” “back,”“horizontal,” “parallel,” “perpendicular,” “vertical,” “lateral,”“coplanar,” and similar terms are used for convenience of describing theattached figures and are not intended to limit this disclosure. Forexample, the terms “left side” and “right side” are used with specificreference to the drawings as illustrated and the embodiments may be inother orientations in use. Further, as used herein, the terms“horizontal,” “parallel,” “perpendicular,” “vertical,” “lateral,” etc.,include slight variations that may be present in working examples.

As used herein, the terms “optical communication,” “in opticalcommunication,” and the like mean that two elements are arranged suchthat optical signals are passively or actively transmittabletherebetween via a medium, such as, but not limited to, an opticalfiber, connectors, free space, index-matching structure or gel,reflective surface, or other light directing or transmitting means.

As used herein, the term “port” means an interface for actively orpassively passing (e.g., receiving, transmitting, or both receiving andtransmitting) optical signals. A port may include, by way ofnon-limiting examples, one or more collimators, pigtails, opticalconnectors, optical splices, optical fibers, free-space, or acombination of the foregoing. In the context of a WDM assembly, a portis the location at which one or more optical signals enters and/or existthe WDM assembly.

As used herein, the term “pigtail” means one or more optical fibers thatextend from a ferrule. The one or more optical fibers may each beterminated with a fiber optical connector but are not required to beterminated with a fiber optic connector.

As used herein, the term “demultiplexed signal” refers to a signalcomponent that can multiplexed with other signal components, whereineach signal component represents a particular wavelength or range ofwavelengths. Thus, a demultiplexed signal may be transmittedindividually or in a multiplexed form.

WDM Assemblies

Disclosed herein is wavelength-division multiplexing (WDM) anddemultiplexing with signal entry and exit in a common/shared routingsurface to increase channel density. That is, signal entry and exitoccurs in the same routing surface. In particular, disclosed is a WDMassembly including one or more common ports and one or more channelsets, with each channel set including one or more channel ports. The WDMassembly further includes a first routing surface with a first WDMpassband and a second routing surface (e.g., with a second WDM passbandor a reflective surface) offset from the first routing surface. Thesecond routing surface is configured to reflect at least one signalpassed through the first routing surface back through the first routingsurface at a laterally different location. The offset between the firstrouting surface and the second routing surface controls a pitch betweensignals reflected from the first routing surface and the second routingsurface, while maintaining a sufficiently large surface area to ensureproper signal performance and/or structural integrity. Controlling pitchby offset provides higher density routing with smaller channel pitchesand/or more channels in a decreased volume. Additionally, theembodiments disclosed herein are easy to manufacture and low cost.

FIGS. 2A-2B are views of embodiments of a WDM assembly 200 (may also bereferred to as a WDM optical assembly). In particular, FIG. 2A is adiagram of a WDM assembly 200 including a first WDM common port 202A(may be referred to generally as WDM common port 202) in opticalcommunication with a first channel set 204A (may be referred togenerally as channel set 204) of two WDM channel ports 206A(1)-206A(2)(each may be referred to generally as a channel port 206) by a pluralityof routing surfaces 208(1)-208(2) (each may be referred to generally asa routing surface 208). The first WDM common port 202A is configured foroptical communication of a first multiplexed signal including a firstsignal λA1 (“first signal component”) and a second signal λA2 (“secondsignal component”). Thus, the first multiplexed signal may be denoted asλA1+λA2 or λA1-λA2 (with the “-” meaning “through”). It is noted thatλA1 and λA2 do not necessarily represent single wavelengths; insteadthey can be groups of wavelengths which can be selectivelypassed/reflected by thin film filter (TFF) wavelength-divisionmultiplexing. Because ultimately the first signal λA1 and the secondsignal λA2 can be demultiplexed, and such demultiplexing is the intentof WDM assemblies according to this disclosure, the first signal λA1 andthe second signal λA2 may alternatively be referred to respectively as a“first demultiplexed signal λA1” and a “second demultiplexed signalλA2.” This terminology may be used for convenience even when the firstsignal λA1 and the second signal λA2 are transmitted in a multiplexedform, i.e., as the first multiplexed signal λA1+λA2.

Still referring to FIGS. 2A-2B, the first channel port 206A(1) of thefirst channel set 204A is configured for optical communication of thefirst demultiplexed signal λA1, and the second channel port 206A(2) ofthe first channel set 204A is configured for optical communication ofthe second demultiplexed signal λA2. The WDM assembly 200 includes afirst WDM common port 202A, a single channel set 204 (in the form of thefirst channel set 204A), and two channel ports 206A(1)-206A(2) forillustrative purposes. In other embodiments, the WDM assembly 200 mayinclude additional WDM common ports 202, channel sets 204, and/orchannel ports 206(1)-206(2).

The routing surfaces 208(1)-208(2) form or otherwise define an opticalpath 210A (may be referred to generally as optical path 210) between thefirst WDM common port 202A and each of the channel ports206A(1)-206A(2). In particular, the first routing surface 208(1) has aunique passband (e.g., via a WDM coating such as a thin film filter) toallow a portion of the optical signal to pass therethrough (e.g., thesecond demultiplexed signal λA2) at an entry lateral location and toreflect the remaining portion of the optical signal (e.g., the firstdemultiplexed signal λA1) at the entry lateral location. In certainembodiments, the passband comprises short-pass, long-pass, and/orband-pass passbands. The second routing surface 208(2) (e.g., a secondpassband and/or a mirror) is configured to reflect the seconddemultiplexed signal λA2 back through the first routing surface 208(1)at an exit lateral location (different from the entry lateral location)of the first routing surface 208(1). It is noted that here andthroughout the disclosure, in certain embodiments, the optical signalpath 210A (may be referred to herein as an optical path, signal path,etc.) is bidirectional between the first WDM common port 202A and thechannel ports 206A(1)-206A(2). In other words, for demux applications,the first WDM common port 202A is an input and the channel ports206A(1)-206A(2) are outputs, and for mux applications the channel ports206A(1)-206A(2) are inputs and the first WDM common port 202A is anoutput.

The optical signal path 210A includes a common port path 212A betweenthe first WDM common port 202A and the first routing surface 208(1), afirst channel path 214A(1) between the first routing surface 208(1) andthe first channel port 206A(1), and a second channel path 214A(2)between the second routing surface 208(2) and the second channel port206A(2). The first channel path 214A(1) and the second channel path214A(2) are generally parallel to each other (i.e., the pitch P betweenthe first channel path 214A(1) and the second channel path 214A(2) isconstant from the first routing surface 208(1) to the respective channelports 206A(1)-206A(2)). In certain embodiments the pitch P could be 87microns or less. It is noted that here and throughout the disclosure, incertain embodiments, the channel paths 214A(1)-214A(2) may be embodiedas lanes (e.g., straight lanes).

The optical signal path 210A of the second demultiplexed signal λA2 isdefined by the first WDM common port 202A, the first routing surface208(1), the at least one second routing surface 208(2), and the secondchannel port 206A(2). The first routing surface 208(1) is positioned inthe optical signal path 210A between the first WDM common port 202A andthe at least one second routing surface 208(2) and between the at leastone second routing surface 208(2) and the second channel port 206A(2).The second routing surface 208(2) is offset from the first routingsurface 208(1) by an offset O, which corresponds to the pitch P betweenthe first channel path 214A(1) and the second channel path 214A(2).

Referring to FIG. 2B, as an example, a different offset O′ correspondsto a different pitch P′ between adjacent channel paths 214A(1)-214A(2).As the offset O′ decreases, the pitch P′ also decreases. In this way,the offset O′ between the first routing surface 208(1) and the secondrouting surface 208(2) controls the pitch P′ between the channel paths214A(1)-214A(2) and corresponding signals reflected from the firstrouting surface 208(1) and the second routing surface 208(2), whilemaintaining a sufficiently large surface area to ensure proper signalperformance and/or structural integrity. Controlling pitch by offsetprovides higher density routing with smaller channel pitches and/or morechannels in a decreased volume.

FIG. 3A is a top view of another embodiment of the WDM assembly of FIGS.2A-2B. A WDM assembly 300 includes a WDM filter 302 with a first routingsurface 304(1) (may also be referred to as a front surface) at a frontof the WDM filter 302, a second routing surface 304(2) (may also bereferred to as a back surface) opposite thereto at a back of the WDMfilter 302, and lateral sides 305A-305B extending between the firstrouting surface 304(1) and the second routing surface 304(2). The firstrouting surface 304(1) has a first unique passband to allow a portion ofthe optical signal to pass therethrough (e.g., the second demultiplexedsignal λA2) and to reflect the remaining portion (e.g., the firstdemultiplexed signal λA1). The second routing surface 304(2) has asecond unique passband to reflect the optical signal that passed throughthe first routing surface 304(1) (e.g., the second demultiplexed signalλA2). However, in certain embodiments, the second routing surface 304(2)instead includes a reflective surface or a mirror.

The angle of incidence θi1 of the first multiplexed signal λA1 is thesame as the angle of refraction θR2 of the second demultiplexed signalλA2 exiting the first routing surface 304(1), and the angle ofrefraction θR1 of the second demultiplexed signal λA2 entering the firstrouting surface 304(1) is the same as the angle of incidence θi2 of thesecond demultiplexed signal λA2 exiting the first routing surface304(1). Accordingly, the first channel path 214A(1) and the secondchannel path 214A(2) are generally parallel to each other from the firstrouting surface 304(1) to the respective channel ports 206A(1)-206A(2)(i.e., the pitch between the first channel path 214A(1) and the secondchannel path 214A(2) is constant).

As similarly noted above, the second routing surface 304(2) is offsetfrom the first routing surface 304(1) by a thickness t1, whichdetermines the pitch P (FIG. 2A) between the first channel path 214A(1)and the second channel path 214A(2). As the thickness t1 decreases, thepitch P also decreases. Thus, the pitch P between adjacent channels canbe altered by changing the thickness t1 of the WDM filter 302 (i.e.,between the first routing surface 304(1) and the second routing surface304(2)) rather than the width of the WDM filter 302 (i.e., betweenlateral sides 305A-305B), which maintains a sufficiently large surfacearea to ensure proper signal performance and/or structural integrity. Incertain embodiments, the thickness t1 of the WDM filter 302 isdetermined by a filter base material index of refraction and opticalbeam angle of incidence Oil.

FIG. 3B is a top view of another embodiment of a WDM assembly 300′including the WDM filter 302 of FIG. 3A. The WDM assembly 300′ includesa first WDM common port 202 in optical communication with a channel set204 of four WDM channel ports 206A(1)-206A(4) by a plurality of routingsurfaces 304(1)-304(4) of the WDM assembly 300′. The first WDM commonport 202 is configured for optical communication of a first multiplexedsignal including a first demultiplexed signal λA1, a seconddemultiplexed signal λA2, a third demultiplexed signal λA3, and a fourthdemultiplexed signal λA4. Thus, the first multiplexed signal in thisembodiment may be denoted as λA1+λA2+λA3+λA4, or simply λA1−λA4 (withthe “-” meaning “through”). The first channel port 206A(1) is configuredfor optical communication of the first demultiplexed signal λA1. Thesecond channel port 206A(2) is configured for optical communication ofthe second demultiplexed signal λA2. The third channel port 206A(3) isconfigured for optical communication of the third demultiplexed signalλA3. The fourth channel port 206(4) is configured for opticalcommunication of the fourth demultiplexed signal λA4.

The WDM assembly 300′ includes a plurality of filters 302(1)-302(2)and/or substrates 310(1)-310(2) in a stacked orientation (may bereferred to herein as a WDM stack, filter stack, optical subassembly,routing subassembly, WDM subassembly, etc.). The WDM assembly 300′includes a first support substrate 310(1) having a first transmissivesurface 312(1) and a second transmissive surface 312(2) oppositethereto. The first transmissive surface 312(1) is configured to pass thefirst multiplexed signal λA1-λA4 at a refracted angle to the secondtransmissive surface 312(2), which is also configured to pass the firstmultiplexed signal λA1. In certain embodiments, the first transmissivesurface 312(1) includes an anti-reflective coating. It is noted thatthroughout the specification, any transmissive surface may include ananti-reflective coating and any routing surface may include a WDMcoating (e.g., a thin film filter).

The WDM assembly 300′ further includes a first WDM filter 302(1) of theplurality of filters 302(1)-302(2) including a first routing surface304(1) including a first unique passband and a second routing surface304(2) opposite thereto including a second unique passband. The firstrouting surface 304(1) is proximate (e.g., contacting) the secondtransmissive surface 312(2) of the first support substrate 310(1). Thefirst routing surface 304(1) is configured to reflect the firstdemultiplexed signal λA1 and pass the second, third, and fourthdemultiplexed signals λA2-λA4. The reflected first demultiplexed signalλA1 proceeds back through the first transmissive surface 312(1) of thefirst support substrate 310(1). The second routing surface 304(2) isconfigured to reflect the second demultiplexed signal λA2 and pass thethird and fourth demultiplexed signals λA3-λA4. The reflected seconddemultiplexed signal λA2 proceeds back through the first routing surface304(1) and the first transmissive surface 312(1), exiting each surfaceat a different lateral location than entry.

The WDM assembly 300′ further includes a second support substrate 310(2)including a third transmissive surface 312(3) and a fourth transmissivesurface 312(4) opposite thereto. The third and fourth transmissivesurfaces 312(3)-312(4) are configured to pass the third and fourthdemultiplexed signals λA3-λA4.

The WDM assembly 300′ further includes a second WDM filter 302(2)including a third routing surface 304(3) including a third uniquepassband and a fourth routing surface 304(4) opposite thereto includinga fourth unique passband. The third routing surface 304(3) is proximate(e.g., contacting) the third transmissive surface 312(3) of the secondsupport substrate 310(2). The third routing surface 304(3) is configuredto reflect the third demultiplexed signal λA3 and pass the fourthdemultiplexed signal λA4. The reflected third demultiplexed signal λA3proceeds back through the second routing surface 304(2), first routingsurface 304(1), and first transmissive surface 312(1) of the firstsupport substrate 310(1). The fourth routing surface 304(4) isconfigured to reflect the fourth demultiplexed signal λA4. The reflectedfourth demultiplexed signal λA4 proceeds back through the third routingsurface 304(3), the second routing surface 304(2), the first routingsurface 304(1), and the first transmissive surface 312(1), exiting eachsurface at a different lateral location than entry.

Each of the demultiplexed signals λA1-λA4 proceeds from the firsttransmissive surface 312(1) along their respective channel path214A(1)-214A(4) to their respective channel port 206A(1)-206A(4). It isnoted that the thickness t1 of the first support substrate does notaffect the pitch between the channel paths 214A(1)-214A(4). Instead, thepitch P1 between the first channel path 214A(1) and the second channelpath 214A(2) is determined by a thickness t2 of the first WDM filter302(1). The pitch P2 between the second channel path 214A(2) and thethird channel path 214A(3) is determined by a thickness t3 of the secondsupport substrate 310(2). The pitch P3 between the third channel path214A(3) and the fourth channel path 214A(4) is determined by a thicknesst4 of the second WDM filter 302(2).

FIG. 4A is a top view of another embodiment of the WDM assembly of FIGS.2A-2B. A WDM assembly 400 (may be referred to herein as a WDM stack,filter stack, optical subassembly, routing subassembly, WDM subassembly,etc.) includes a first WDM filter 402(1) having a thickness t1 and asecond WDM filter 402(2) having a thickness t2. The first WDM filter402(1) includes a first transmissive surface 404(1) at a front and afirst routing surface 304(1) at a back opposite thereto. The firsttransmissive surface 404(1) is positioned in the optical signal path210A between the first WDM common port 202 and the first routing surface304(1). In certain embodiments, the first transmissive surface 404(1)includes an anti-reflective coating. Similarly, the second WDM filter402(2) includes a second transmissive surface 404(2) at a front and asecond routing surface 304(2) at a back opposite thereto. The secondtransmissive surface 404(2) of the second WDM filter 402(2) ispositioned proximate the first routing surface 304(1) of the first WDMfilter 402(1).

FIG. 4B is a top view of the WDM filters of FIG. 4A illustratingconstant signal pitch P with a different thickness t1′ of the first WDMfilter 402(1). The thickness t1′ of the first WDM filter 402(1) betweenthe first transmissive surface 404(1) and the first routing surface304(1) is greater than the thickness t2 of the second WDM filter 402(2)between the second transmissive surface 404(2) and the second routingsurface 304(2). As shown, increasing the thickness of the first WDMfilter 402(1) laterally shifts the first and second channel paths214A(1)-214A(2) but does not affect the pitch P between them.

FIG. 4C is a top view of the WDM filters of FIG. 4A illustrating adifferent signal pitch P′ with a different thickness t2′ of the secondWDM filter 402(2). The thickness t2′ of the second WDM filter 402(2)between the second transmissive surface 404(2) and the second routingsurface 304(2) is decreased compared to FIG. 4A. As shown, decreasing(or otherwise changing) the thickness t2′ of the second WDM filter402(2) does not laterally shift the first channel path 214A(1) but doeslaterally shift the second channel path 214A(2) to decrease (orotherwise change) the pitch P′ between them. In other words, the pitchP′ between the signal paths of the first demultiplexed signal λA1 andthe second demultiplexed signal λA2 exiting the first routing surface304(1) is defined by the thickness t2′ of the second WDM filter 402(2).

FIG. 4D is a top view of another embodiment of the WDM assemblyincluding the WDM filters of FIGS. 4A-4C. A WDM assembly 400′ is similarto the WDM assembly 300′ of FIG. 3B except where otherwise noted. TheWDM assembly 400′ includes a plurality of WDM filters 402(1)-402(4) (andno support substrate) in a stacked orientation. In particular, the WDMassembly 400′ includes a plurality of WDM filters 402(1)-402(4), eachwith a transmissive surface 404(1)-404(4) at a front and a routingsurface 304(1)-304(4) at a back opposite thereto.

The first routing surface 304(1) of the first WDM filter 402(1) isproximate (e.g., contacting) the second transmissive surface 404(2) ofthe second WDM filter 402(2). The reflected first demultiplexed signalλA1 reflected by the first routing surface 304(1) proceeds back throughthe first transmissive surface 404(1) of the first WDM filter 402(1),exiting at a different lateral location than entry.

The second routing surface 304(2) of the second WDM filter 402(2) isproximate (e.g., contacting) the third transmissive surface 404(3) ofthe third WDM filter 402(3). The reflected second demultiplexed signalλA2 reflected by the first routing surface 304(1) proceeds back throughthe first WDM filter 402(1) (i.e., the first routing surface 304(1) andthe first transmissive surface 404(1)) exiting the first WDM filter402(1) at a different lateral location than entry.

The third routing surface 304(3) of the third WDM filter 402(3) isproximate (e.g., contacting) the fourth transmissive surface 404(4) ofthe fourth WDM filter 402(4). The reflected third demultiplexed signalλA3 reflected by the first routing surface 304(1) proceeds back throughthe second WDM filter 402(2) (i.e., the second routing surface 304(2)and the second transmissive surface 404(2)) and the first WDM filter402(1) (i.e., the first routing surface 304(1) and the firsttransmissive surface 404(1)), exiting each WDM filter 402(1)-402(2) at adifferent lateral location than entry.

The reflected fourth demultiplexed signal λA4 reflected by the fourthrouting surface 304(4) proceeds back through the third WDM filter 402(3)(i.e., the third routing surface 304(3) and the third transmissivesurface 404(3)), the second WDM filter 402(2) (i.e., the second routingsurface 304(2) and the second transmissive surface 404(2)), and thefirst WDM filter 402(1) (i.e., the first routing surface 304(1) and thefirst transmissive surface 404(1)), exiting each WDM filter402(1)-402(3) at a different lateral location than entry.

Each of the demultiplexed signals λA1-λA4 proceeds from the firsttransmissive surface 404(1) of the first WDM filter 402(1) along theirrespective channel path 214A(1)-214A(4) to their respective channel port206A(1)-206A(4). It is noted that the thickness t1′ of the first WDMfilter 402(1) does not affect the pitch between the channel paths214(1)-214(4). Accordingly, the thickness t1′ of the first WDM filter402(1) can be increased to act as a supporting substrate to theremaining WDM filters 402(2)-402(4). The pitch P1 between the firstchannel path 214(1) and the second channel path 214A(2) is determined bya thickness t2 of the second WDM filter 402(2). The pitch P2 between thesecond channel path 214A(2) and the third channel path 214(3) isdetermined by a thickness t3 of the third WDM filter 402(3). The pitchP3 between the third channel path 214(3) and the fourth channel path214(4) is determined by a thickness t4 of the fourth WDM filter 402(4).

FIG. 4E is a top view of another embodiment of the WDM assembly of FIG.4D. A WDM assembly 400″ is similar to the WDM assembly 400′ of FIG. 4Dexcept where otherwise noted. The WDM assembly 400″ includes a pluralityof WDM filters 402(1)″, 402(2)-402(4) (and no support substrate) in astacked orientation. In particular, the WDM assembly 400″ includes aplurality of WDM filters 402(1)″, 402(2)-402(4), each of WDM filters402(2)-402(4) including a transmissive surface 404(2)-404(4) at a frontand a routing surface 304(2)-304(4) at a back opposite thereto.

The first WDM filter 402(1)″ has a triangular cross-section (as with aprism) including a first transmissive surface 404(1), a routing surface304(1) at an angle (e.g., 90 degree angle) relative to the firsttransmissive surface 404(1), and a reflective surface 406. The firstrouting surface 304(1) of the first WDM filter 402(1)″ is proximate(e.g., contacting) the second transmissive surface 404(2) of the secondWDM filter 402(2). The optical signal path 210A (including the commonport path 212A and channel paths 214A(1)-214A(4)) are routed between thefirst transmissive surface 404(1) and the angled routing surface 304(1)by the reflective surface 406 (e.g., by total internal reflection). Thefirst transmissive surface 404(1) is positioned in the optical signalpath 210A between the first common port path 212A and the at least onefirst routing surface 304(1). The reflective surface 406 is positionedin the optical signal path 210A between the first transmissive surface404(1) and the at least one first routing surface 304(1). In otherwords, for example, the common port path 212A enters a side of the WDMassembly 400″. This may be beneficial depending on space constraints.For example, such a configuration may be used where the first WDM commonport 202A and channel ports 206A(1)-206A(4) are positioned beneath theWDM assembly 400″, so that the stack extends horizontally and the heightof the WDM assembly 400″ can thereby be reduced compared to WDM assembly400′ of FIG. 4D.

FIG. 5 is a top view of another embodiment of the WDM assembly of FIGS.2A-2B. A WDM assembly 500 includes multiple WDM common ports 202A-202Dincluding a first WDM common port 202A, a second WDM common port 202B, athird WDM common port 202C, and a fourth WDM common port 202D in opticalcommunication with, respectively, a first channel set 204A of two WDMchannel ports 206A(1)-206A(2), a second channel set 204B of two WDMchannel ports 206B(1)-206B(2), a third channel set 204C of two WDMchannel ports 206C(1)-206C(2), and a fourth channel set 204D of two WDMchannel ports 206D(1)-206D(2).

The first WDM common port 202A is configured for optical communicationwith the first channel set 204A of the two WDM channel ports206A(1)-206A(2). The first WDM common port 202A is configured foroptical communication of a first multiplexed signal λA1+λA2 including afirst demultiplexed signal λA1 and a second demultiplexed signal λA2.The second WDM common port 202B is configured for optical communicationwith the second channel set 204B of the two WDM channel ports206B(1)-206B(2). The second WDM common port 202B is configured foroptical communication of a second multiplexed signal λB1+λB2 including afirst demultiplexed signal λB1 and a second demultiplexed signal λB2.The third WDM common port 202C is configured for optical communicationwith the third channel set 204C of the two WDM channel ports206C(1)-206C(2). The third WDM common port 202C is configured foroptical communication of a third multiplexed signal λC1+λC2 including afirst demultiplexed signal λC1 and a second demultiplexed signal λC2.The fourth WDM common port 202D is configured for optical communicationwith the fourth channel set 204D of the two WDM channel ports206D(1)-206D(2). The fourth WDM common port 202D is configured foroptical communication of a fourth multiplexed signal λD1+λD2 including afirst demultiplexed signal λD1 and a second demultiplexed signal λD2.

The WDM assembly 500 includes a WDM filter 502 having a first routingsurface 304(1) at a front and a first transmissive surface 404(1) at aback opposite thereto. The WDM assembly 500 further includes a mirror504 having a second routing surface 304(2) at a front. It is noted thatin certain embodiments, the WDM assembly includes a second WDM filterinstead of a mirror 504. The second routing surface 304(2) of the mirror504 is proximate (e.g., contacting) the first transmissive surface404(1) of the WDM filter 502. The first routing surface 304(1) ispositioned in optical signal paths 210A-210D between the WDM commonports 202A-202D and the first transmissive surface 404(1). The firstrouting surface 304(1) is configured to reflect the first demultiplexedsignal λA1-λD1 of each multiplexed signal. The second routing surface304(2) is configured to reflect the second demultiplexed signal λA2-λD2of each multiplexed signal through the first routing surface 304(1).

Each of the optical signal paths 210A-210D enter the same first routingsurface 304(1) at a different lateral location and are reflected by thesame mirror 504 at a different lateral location. Accordingly, a width W1of the first WDM filter 502 and/or a width W2 of the mirror 504 can beshortened or extended to accommodate any number of common ports. Asshown, the width W1 of the first WDM filter 502 can be a different size(e.g., larger) than the width W2 of the mirror 504. It is noted that themirror 504 could be one large mirror 504 (as shown) or individual mirrorelements.

With the multiple WDM common ports 202A-202D, the thickness t1 of theWDM filter 502 controls the pitch PA1 between the first channel path214A(1) and the second channel path 214A(2) of the first channel set204A, but also between the second channel path 214A(2) of the firstchannel set 204A and the first channel path 214B(1) of the secondchannel set 204B. In other words, as the thickness t2 of the WDM filter502 changes, the first channel paths 214A(1)-214D(1) remain stationarybut the position of the second channel paths 214A(2)-214D(2) laterallyshifts in between the first channel paths 214A(1)-214D(1).

FIG. 6A is a top view of another embodiment of the WDM assembly of FIGS.2A-2B. A WDM assembly 600 includes multiple WDM common ports 202A-202Din optical communication with, respectively, channel sets 204A-204D. TheWDM assembly 600 includes a WDM filter 602 having a first transmissivesurface 404(1) at a front and a first routing surface 304(1) at a backopposite thereto.

The WDM assembly 600 further includes a mirror 604 having a secondrouting surface 304(2) at a front. It is noted that in certainembodiments, the WDM assembly 600 includes a second WDM filter insteadof a mirror 604. The second routing surface 304(2) of the mirror 604 isproximate (e.g., contacting) but offset by a thickness O1 from the firstrouting surface 304(1) of the WDM filter 602. The first transmissivesurface 404(1) is positioned in optical signal paths 210A-210D betweenthe WDM common ports 202A-202D and the first routing surface 304(1). Thefirst routing surface 304(1) is configured to reflect a firstdemultiplexed signal λA1-λD1 of each multiplexed signal. The secondrouting surface 304(2) is configured to reflect a second demultiplexedsignal λA2-λD2 of each multiplexed signal through the first routingsurface 304(1).

Each of the optical signal paths 210A-210D enter the same first routingsurface 304(1) at a different lateral location, and are reflected by thesame mirror 604 at a different lateral location. The mirror 604 could beone large mirror 604 (as shown) or individual mirror elements. Eventhough the mirror 604 is offset and does not directly contact the firstWDM filter 602, because the first routing surface 304(1) is generallyparallel with the second routing surface 304(2) and the reflected signalpath proceeds back through the first WDM filter 602, the channel paths214A(1)-214D(2) are generally parallel with one another upon exiting thefirst WDM filter 602. Further, the offset O1 enables active preciseoptical alignment optimization because for extremely small pitches, itmay be more challenging to control the critical thickness of a WDMfilter than to control relative spacing between the first WDM filter 602and the second routing surface 304(2) (of a mirror or a second WDMfilter).

FIG. 6B is a top view of another embodiment of the WDM assembly 600 ofFIG. 6A. A WDM assembly 600′ includes a first routing surface 304(1) ata back of a first WDM filter 602. Instead of a single mirror 604, asecond routing surface includes a plurality of routing surfaces304A(2)-304D(2) of an array 606 of a plurality of mirrors 604A-604Doffset from the first routing surface 304(1) of the first WDM filter602. In particular, the second routing surface 304(2) includes a primarysecond routing surface 304A(2) of a primary mirror 604A to reflect asecond demultiplexed signal λA2 of the first demultiplexed signal, asecondary second routing surface 304B(2) of a secondary mirror 604B toreflect a second demultiplexed signal λB2 of the second demultiplexedsignal, a tertiary second routing surface 304C(2) of a tertiary mirror604C to reflect a second demultiplexed signal λC2 of the thirddemultiplexed signal, and a quaternary second routing surface 304D(2) ofa quaternary mirror 604D to reflect a second demultiplexed signal λD2 ofthe fourth demultiplexed signal. Each mirror 604A-604D is associatedwith a different WDM common port 202A-202D. Using individual separatemirrors 604A-604D provides greater control of individual second channelpaths 214A(2)-214D(2) as each mirror 604A-604D can be rotated around arespective center axis A1-D1 and/or laterally shifted for fine tuning.In other words, one or more of the second routing surfaces304A(2)-304D(2) may not be perfectly aligned or parallel with oneanother. Such a configuration may provide increased freedom of alignmentand best optical performance.

FIG. 7 is a top view of another embodiment of the WDM assembly of FIGS.2A-6B. A WDM assembly 700 includes routing surfaces 304(1)-304(4) in astacked orientation for routing four multiplexed signals from four WDMcommon ports 202A-202D to four channel sets 204A-204D respectively. Forexample, this configuration could incorporate features of theconfigurations of FIGS. 3A-4D. The WDM assembly 700 with the routingsurfaces 304(1)-304(4) in a stacked orientation may be easier andcheaper to manufacture. As shown, the WDM assembly 700 could incorporateadditional WDM common ports 202A-202D simply by extending the width ofthe routing surfaces 304(1)-304(4).

The first WDM common port 202A is configured for optical communicationof a first multiplexed signal including demultiplexed signals λA1-λA4.The first WDM common port 202A is configured for optical communicationwith a first channel set 204A of four WDM channel ports 206A(1)-206A(4).The second WDM common port 202B is configured for optical communicationof a second multiplexed signal including demultiplexed signals λB1-λB4.The second WDM common port 202B is configured for optical communicationwith a second channel set 204B of four WDM channel ports206B(1)-206B(4). The third WDM common port 202C is configured foroptical communication of a third multiplexed signal includingdemultiplexed signals λC1-λC4. The third WDM common port 202C isconfigured for optical communication with a third channel set 204C offour WDM channel ports 206C(1)-206C(4). The fourth WDM common port 202Dis configured for optical communication of a fourth multiplexed signalincluding demultiplexed signals λD1-λD4. The fourth WDM common port 202Dis configured for optical communication with a fourth channel set 204Dof four WDM channel ports 206D(1)-206D(4).

FIGS. 8A and 8B are top views of another embodiment of the WDM assemblyof FIGS. 2A-6B. A WDM assembly 800 includes routing surfaces 304(1),304(1)′, 304(1)″ in a cascaded orientation for routing four multiplexedsignals from four WDM common ports 202A-202D to four channel sets204A-204D respectively. A WDM assembly 800 with routing surfaces and/orindividual second routing surfaces in a cascaded orientation may providemore flexibility with individualized tuning and better opticalperformance. As shown, the WDM assembly 800 could incorporate additionalWDM common ports 202A-202D simply by extending the width of the routingsurfaces 304(1)-304(1)″.

The WDM assembly 800 includes three WDM subassemblies 802, 802′, 802″configured to demultiplex four signals. As similarly discussed withrespect to FIG. 6B, each WDM subassembly 802, 802′, 802″ includes a WDMfilter 602, 602′, 602″ with a first routing surface 304(1), 304(1)′,304(1)″ at a back of the WDM filter 602, 602′, 602″. Each WDMsubassembly 802, 802′, 802″ includes an array 606, 606′, 606″ of aplurality of mirrors 604A-604D, 604A′-604D′, 604A″-604D″ with respectivesecond routing surfaces 304A(2)-304D(2), 304A(2)′-304D(2)′,304A(2)″-304D(2)″ offset from the first routing surfaces 304(1),304(1)′, 304(1)″ of the WDM filters 602, 602′, 602″.

The first WDM subassembly 802 receives the multiplexed signals from WDMcommon ports 202A-202D and demultiplexes the first demultiplexed signalsλA1-λD1 therefrom. The first routing surface 304(1) of the first WDMsubassembly 802 reflects the first demultiplexed signals λA1-λD1. Thesecond routing surface 304A(2)-304D(2) of the first WDM subassembly 802respectively reflects the second, third, and fourth demultiplexedsignals λA2-λD4. The second WDM subassembly 802′ receives thedemultiplexed signals λA1-λD1 and multiplexed signals λA2-λD4 from thefirst WDM subassembly 802 and demultiplexes the second demultiplexedsignal λA2-λD2 therefrom. The first routing surface 304(1)′ of thesecond WDM subassembly 802′ reflects the first demultiplexed signalλA1-λD1 and the second demultiplexed signal λA2-λD2. The second routingsurfaces 304A(2)′-304D(2)′ of the second WDM subassembly 802′respectively reflect the third and fourth demultiplexed signals λA3-λD4.The third WDM subassembly 802″ receives the demultiplexed signalsλA1-λD2 and multiplexed signals λA3-λD4 from the second WDM subassembly802′ and demultiplexes the third demultiplexed signal λA3-λD3 therefrom.The first routing surface 304(1)″ of the third WDM subassembly 802″reflects the first demultiplexed signal λA1-λD1, the seconddemultiplexed signal λA2-λD2, and the third demultiplexed signalλA3-λD3. The second routing surfaces 304A(2)″-304D(2)″ of the third WDMsubassembly 802″ respectively reflect the fourth demultiplexed signalsλA4-λD4. Thus, the channel sets 204A-204D receive demultiplexed signalsλA1-λD4 from the third WDM subassembly 802″.

FIGS. 9A-9C are views of another embodiment of the WDM assembly of FIGS.2A-7 routing parallel signal paths offset from each other in a lateraldirection. A WDM assembly 900 (or WDM stack) is parallel arrayed (mayalso be referred to as a three-dimensional array) and includes routingsurfaces 304(1)-304(4) in a stacked orientation for routing fourmultiplexed signals from four WDM common ports 202A-202D to four channelsets 204A-204D respectively (see FIG. 7). In particular, channel set204A includes channel ports 206A(1)-206A(4), channel set 204B includeschannel ports 206B(1)-206B(4), channel set 204C includes channel ports206C(1)-206C(4), and channel set 204D includes channel ports206D(1)-206D(4). For example, this configuration could incorporatefeatures of the configurations of FIGS. 3A-4D. FIGS. 9A-9C incorporatesimilar features as those of FIG. 7, except where otherwise noted, butmay omit labeling certain features for drawing clarity.

The WDM assembly 900 with routing surfaces in a stacked orientation maybe easier and cheaper to manufacture, such as due to the passive natureof the mux/demux. In certain embodiments, the WDM assembly 900 canintegrate with a vertical grating coupler array. The WDM assembly 900may be used for small pitch, high channel count applications. As shown,the WDM assembly 900 could incorporate additional WDM common ports202A-202D simply by extending the width W and/or depth D of the routingsurfaces 304(1)-304(4).

Referring to FIGS. 9A-9B, the first WDM common port 202A is configuredfor optical communication of a first multiplexed signal includingdemultiplexed signals λA1-λA4. The first WDM common port 202A isconfigured for optical communication along a first signal path with thefirst channel set 204A of four WDM channel ports 206A(1)-206A(4) withina first signal plane SP(A). The second WDM common port 202B isconfigured for optical communication of a second multiplexed signalincluding demultiplexed signals λB1-λB4. The second WDM common port 202Bis configured for optical communication along a second signal path withthe second channel set 204B of four WDM channel ports 206B(1)-206B(4)within a second signal plane SP(B). The third WDM common port 202C isconfigured for optical communication of a third multiplexed signalincluding demultiplexed signals λC1-λC4. The third WDM common port 202Cis configured for optical communication along a third signal path withthe third channel set 204C of four WDM channel ports 206C(1)-206C(4)within a third signal plane SP(C). The fourth WDM common port 202D isconfigured for optical communication of a fourth multiplexed signalincluding demultiplexed signals λD1-λD4. The fourth WDM common port 202Dis configured for optical communication along a fourth signal path withthe fourth channel set 204D of four WDM channel ports 206D(1)-206D(4)within a fourth signal plane SP(D). The signal paths within the signalplanes SP(A)-SP(D) are parallel to and offset from each other. Thesignal paths extend along a width W of the WDM assembly 900 but arepositioned adjacent to and offset from each other along a depth D of theWDM assembly.

Referring to FIGS. 9A and 9C, in certain embodiments, the WDM commonports 202A-202D are aligned in a common port plane CMP, which extendsperpendicular to the signal planes SP(A)-SP(D). In certain embodiments,the channel ports 206A(1)-206D(4) within each channel set 204A-204D arealigned within the respective signal planes SP(A)-SP(D). In certainembodiments, the first channel ports 206A(1)-206D(1) of each channel set204A-204D are aligned along a first channel plane CP(1) perpendicular tothe signal planes SP(A)-SP(D). The second channel ports 206A(2)-206D(2),third channel ports 206A(3)-206D(3), and fourth channel ports206A(2)-206D(2) of each channel set 204A-204D are similarly configured(i.e., aligned respectively) along channel planes CP(2)-CP(4). Thus, incertain embodiments, the channel ports 206A(1)-206D(4) of the channelsets 204A-204D are positioned in a grid array. In certain embodiments,such a configuration may increase the channel density and decrease theform factor (e.g., footprint).

In certain embodiments, each routing surface 304(1)-304(4) includes asingle continuous routing surface 304(1)-304(4). As similarly explainedwith respect to FIGS. 3A-3B, such a configuration maintains asufficiently large surface area to ensure proper signal performanceand/or structural integrity. Further, such a configuration may decreasemanufacturing costs and design complexity.

FIG. 10 is a view of another embodiment of the WDM assembly of FIGS.2A-7. In particular, WDM assembly 1000 includes a plurality of WDMsubassemblies 1002A-1002D (or WDM stacks), each routing one of aplurality of parallel and offset signal paths. In particular, the WDMassembly 1000 incorporates features and functionality described withrespect to the WDM assembly 900 of FIGS. 9A-9C except where otherwisenoted. As similarly noted above, FIG. 10 incorporates similar featuresas those of FIGS. 9A-9C except where otherwise noted, but may omitlabeling certain features for drawing clarity.

Each of the WDM subassemblies 1002A-1002D are positioned adjacent to oneanother. In this way, a first routing surface 304(1) includes aplurality of routing surfaces 304A(1)-304D(1), a second routing surface304(2) includes a plurality of routing surfaces 304A(2)-304D(2), a thirdrouting surface 304(3) includes a plurality of routing surfaces304A(3)-304D(3), and a fourth routing surface 304(4) includes aplurality of routing surfaces 304A(4)-304D(4). For example, between theplurality of WDM subassemblies 1002A-1002D, the first routing surface304(1) includes a primary first routing surface 304A(1), a secondaryfirst routing surface 304B(1), a tertiary first routing surface 304C(1),and a quaternary first routing surface 304D(1).

Instead of a single WDM stack, the plurality of WDM stacks 1002A-1002Dmay provide more flexibility and/or customization in design. Forexample, each of the WDM stacks 1002A-1002D may include routing surfaces304(1)-304(4) with passbands that differ between the WDM stacks1002A-1002D. In other words, each of the WDM stacks 1002A-1002D mayinclude a unique combination of routing surfaces 304(1)-304(4) relativeto the other WDM stacks 1002A-1002D.

FIGS. 11A-11C are views of a bottom surface 404(1) of a WDM filter402(1) of WDM assemblies 1100, 1102, 1104 illustrating differentconfigurations and signal paths. It is noted that for clarity, WDMcommon ports 202A-202D and channel ports 206A(1)-206D(4) are not shownin FIGS. 11A-11C, but refer to features previously described. Inparticular, each of FIGS. 11A-11C illustrate intersection of signalpaths of WDM common ports 202A-202D and channel ports 206A(1)-206D(4)with the bottom surface 404(1) of the WDM filter 402(1) of a WDM filterstack. In other words, each illustrate entry locations and exitlocations (see, e.g., FIG. 3A) of signal paths of WDM common ports202A-202D and channel ports 206A(1)-206D(4). Signal paths of WDM commonports 202A-202D propagate through the bottom surface 404(1) at positions212A-212D and signal paths of channel ports 206A(1)-206D(4) propagatethrough the bottom surface 404(1) at positions 214A(1)-214D(4). Incertain embodiments, the pattern of intersections of the signal pathswith the bottom surface 404(1) may generally correspond to a layout ofthe respective WDM common ports 202A-202D and channel ports206A(1)-206D(4). Thus, references to WDM common ports 202A-202D andchannel ports 206A(1)-206D(4) will continue to be made below in furtherdescribing FIGS. 11A-11C, but as noted above, only correspondingpositions 212A-212D and 214A(1)-214D(4) are illustrated in FIGS.11A-11C.

In particular, FIG. 11A is a bottom view of a bottom surface 404(1) of aWDM filter 402(1) of a WDM filter stack illustrating a planarconfiguration of WDM common ports 202A-202D and signal paths, such as ofthe WDM assembly 700 of FIG. 7. As shown, the WDM common ports 202A-202Dand channel ports 206A(1)-206D(4) are aligned along a single plane suchthat the signal paths 210A-210D (including positions 212A-214D(4))intersect with the bottom surface 404(1) along a single plane P11.

FIG. 11B is a bottom view of a bottom surface 404(1) of a WDM filter402(1) of a WDM filter stack illustrating a parallel and offsetconfiguration of WDM common ports 202A-202D (represented by positions212A-212D) and signal paths of the WDM assembly of FIGS. 9A-9C. Asshown, first WDM common port 202A and respective channel ports206A(1)-206A(4) are aligned along a first plane such that the signalpath 210A (including positions 212A-214A(4)) intersects with the bottomsurface 404(1) along a first plane P11(1), second WDM common port 202Band respective channel ports 206B(1)-206B(4) are aligned along a secondplane such that the signal path 210A (including positions 212B-214B(4))intersects with the bottom surface 404(1) along a second plane P11(2),third WDM common port 202C and respective channel ports 206C(1)-206C(4)are aligned along a third plane such that the signal path 210C(including positions 212C-214C(4)) intersects with the bottom surface404(1) along a third plane P11(3), and fourth WDM common port 202D andrespective channel ports 206D(1)-206D(4) are aligned along a fourthplane such that the signal path 210D (including positions 212D-214D(4))intersects with the bottom surface 404(1) along a fourth plane P11(4).The positions 212A-212D are aligned along a plane perpendicular to thesignal planes P11(1)-P11(4). The first channel ports 206A(1)-206D(1),the second channel ports 206A(2)-206D(2), the third channel ports206A(3)-206D(3), and the fourth channel ports 206A(2)-206D(2) of eachchannel set 204A-204D may be similarly arranged (i.e., aligned alongrespective planes that are perpendicular to the signal planesP11(1)-P11(4)) due to the grid array provided by the WDM common ports202A-202D and channel ports 206A(1)-206D(4) (see discussion of FIG. 9Cabove).

FIG. 11C is a bottom view of a bottom surface 404(1) of a WDM filter402(1) of a WDM filter stack illustrating a different grid array of WDMcommon ports 202A-202D and signal paths combining features of the WDMassembly of FIGS. 7 and 9A-9C. In particular, common ports 212A, 212Band respective channel ports 206A(1)-206B(4) are aligned along a firstplane such that the signal paths 210A-210B (including positions 212A,212B, 214A(1)-214B(4)) intersect with the bottom surface 404(1) along afirst plane P11(1)′, and common ports 212C, 212D and respective channelports 206C(1)-206D(4) are aligned along a second plane such that thesignal paths 210C-210D (including positions 212C, 212D, 214C(1)-214D(4))intersect with the bottom surface 404(1) along a second plane P11(2)′.The positions 212A, 212B, 214A(1)-214B(4) are aligned respectively withthe positions 212C, 212D, 214C(1)-214D(4) in planes perpendicular to thefirst and second planes P11(1)′, P11(2)′. In other words, the positions212A-214D(4) are arranged in a grid because the common ports 212A-212Dand respective channel ports 206A(1)-206D(4) may be similarly arranged.Each of the common ports 212A-212D are configured to define a respectiveoptical signal path through the at least one first routing surface. Eachof the channel ports 206A(1)-206D(4) are configured to define arespective optical signal path through the at least first routingsurface.

It is noted that, here and throughout the disclosure, more or fewer WDMcommon ports 202A-202D and/or channel ports 206A(1)-206D(4) may be used(e.g., to produce a larger grid arrangement).

FIG. 12 is a perspective view of another embodiment of the WDM assemblyof FIGS. 2A-6B and 8A-8B routing parallel and offset signal paths in acascaded orientation. Similar to the WDM assembly 800 of FIGS. 8A-8B,the WDM assembly 1200 includes routing surfaces 304(1), 304(1)′, 304(1)″in a cascaded orientation for routing four multiplexed signals from fourWDM common ports 202A-202D to four channel sets 204A-204D respectively.The WDM assembly 1200 with routing surfaces and/or individual secondrouting surfaces in a cascaded orientation may provide more flexibilitywith individualized tuning and the overall better optical performance.

The WDM assembly 1200 includes three WDM subassemblies 1202, 1202′,1202″ configured to demultiplex four signals. Each WDM subassembly 1202,1202′, 1202″ includes a WDM filter 602, 602′, 602″ with a first routingsurface 304(1), 304(1)′, 304(1)″ at a back of the WDM filter 602, 602′,602″. Each WDM subassembly 1202, 1202′, 1202″ includes a second WDMfilter 1204, 1204′, 1204″ with a second routing surfaces 304(2),304(2)′, 304(2)″ offset from the first routing surfaces 304(1), 304(1)′,304(1)″ of the WDM filters 602, 602′, 602″. The WDM filters 602, 602′,602″ of the WDM subassemblies 1202, 1202′, 1202″ are positioned adjacentto one another. In certain embodiments, the WDM filters 602, 602′, 602″abut the sides of one another. Further, in such a configuration, everyother of the WDM filters 602, 602′, 602″ is inverted such that, forexample, a transmissive surface 404′ of WDM filter 602′ is proximate andpositioned between the first routing surfaces 304(1), 304(1)″ of the WDMfilters 602, 602″.

The first WDM subassembly 1202 receives the multiplexed signals from WDMcommon ports 202A-202D through a transmissive surface 404 of the WDMfilter 602 and demultiplexes the first demultiplexed signals λA1-λD1therefrom. The first routing surface 304(1) of the first WDM subassembly1202 reflects the first demultiplexed signals λA1-λD1. The secondrouting surface 304(2) of the first WDM subassembly 1202 respectivelyreflects the second, third, and fourth demultiplexed signals λA2-λD4.The second WDM subassembly 1202′ receives the demultiplexed signalsλA1-λD1 and multiplexed signals λA2-λD4 from the first WDM subassembly1202 through sides of the WDM filters 602, 602′ and demultiplexes thesecond demultiplexed signal λA2-λD2 therefrom. The first routing surface304(1)′ of the second WDM subassembly 1202′ reflects the firstdemultiplexed signal λA1-λD1 and the second demultiplexed signalλA2-λD2. The second routing surface 304(2)′ of the second WDMsubassembly 1202′ respectively reflects the third and fourthdemultiplexed signals λA3-λD4. The third WDM subassembly 1202″ receivesthe demultiplexed signals λA1-λD2 and multiplexed signals λA3-λD4 fromthe second WDM subassembly 1202′ through sides of the WDM filters 602′,602″ and demultiplexes the third demultiplexed signal λA3-λD3 therefrom.The first routing surface 304(1)″ of the third WDM subassembly 1202″reflects the first demultiplexed signal λA1-λD1, the seconddemultiplexed signal λA2-λD2, and the third demultiplexed signalλA3-λD3. The second routing surface 304(2)″ of the third WDM subassembly1202″ respectively reflects the fourth demultiplexed signals λA4-λD4through the transmissive surface 404″ of the WDM filter 602″. Thus, thechannel sets 204A-204D receive demultiplexed signals λA1-λD4 from thethird WDM subassembly 1202″.

FIG. 13A is a flowchart of steps 1300 for using any of the WDMassemblies of FIGS. 2A-12. Step 1302 includes propagating, from a firstcommon port, a first multiplexed signal comprising a first demultiplexedsignal and a second demultiplexed signal. Step 1304 includes reflectingthe first demultiplexed signal of the first multiplexed signal off afirst routing surface having a first passband so that the firstmultiplexed signal is directed to a first channel set including a firstchannel port. Step 1306 includes passing the second demultiplexed signalof the first multiplexed signal through the first routing surface. Step1308 includes reflecting, off at least one second routing surface, thesecond demultiplexed signal that was passed through the first routingsurface. In certain embodiments, the at least one second routing surfacecomprises a second passband. In certain embodiments, the at least onesecond routing surface comprises a mirror. Step 1310 includes passingthe second demultiplexed signal reflected from the at least one secondrouting surface through the first routing surface to a second channelport.

In certain embodiments, the WDM assembly is in a stacked configuration.Accordingly, in certain embodiments, the method further includes passinga third demultiplexed signal of the first multiplexed signal through thefirst routing surface. The method further includes passing the thirddemultiplexed signal through the at least one second routing surface.The method further includes reflecting, off at least one third routingsurface, the third demultiplexed signal passed through the first routingsurface and the at least one second routing surface. The method furtherincludes passing the third demultiplexed signal of the first multiplexedsignal reflected from the at least one third routing surface through theat least one second routing surface and the at least one first routingsurface to a third channel port of the first channel set.

In certain embodiments, the WDM assembly is in a cascaded configuration.Accordingly, in certain embodiments, the method further includesreflecting, off the at least one second routing surface, the seconddemultiplexed signal of the first multiplexed signal and a thirddemultiplexed signal of the first multiplexed signal. The method furtherincludes reflecting, off at least one third routing surface, the firstdemultiplexed signal of the first multiplexed signal and the seconddemultiplexed signal of the first multiplexed signal. The method furtherincludes passing the third demultiplexed signal of the first multiplexedsignal through the at least one third routing surface.

In certain embodiments, the WDM assembly includes multiple common ports.Accordingly, in certain embodiments, the method further includespropagating, from a second common port, a second multiplexed signalcomprising a first demultiplexed signal and a second demultiplexedsignal. The method further includes reflecting the first demultiplexedsignal of the second multiplexed signal by the first routing surfacehaving the first passband to a first channel port of a second channelset. The method further includes passing the second demultiplexed signalof the second multiplexed signal through the first routing surface. Themethod further includes reflecting, off the at least one second routingsurface, the second demultiplexed signal of the second multiplexedsignal passed through the first routing surface. The method furtherincludes passing the second demultiplexed signal of the secondmultiplexed signal reflected from the at least one second routingsurface through the first routing surface to a second channel port ofthe second channel set.

As similarly noted above, this method may be used with any number ofcommon ports and/or any number of channels.

FIG. 13B is a flowchart 1312 of steps for using any of the WDMassemblies of FIGS. 7-12. Step 1314 includes routing, along a firstoptical signal path in a first signal plane, a first multiplexed signalfrom a first common port to a first channel set. Substep 1316 includespropagating, from a first common port, the first multiplexed signalcomprising a first demultiplexed signal and a second demultiplexedsignal. Substep 1318 includes reflecting the first demultiplexed signalof the first multiplexed signal off at least one first routing surfacehaving a first passband to a first channel port of a first channel set.Substep 1320 includes passing the second demultiplexed signal of thefirst multiplexed signal through the at least one first routing surface.Substep 1322 includes reflecting, off at least one second routingsurface, the second demultiplexed signal of the first multiplexed signalpassed through the at least one first routing surface. Substep 1324includes passing the second demultiplexed signal of the firstmultiplexed signal reflected from the at least one second routingsurface through the at least one first routing surface to a secondchannel port of the first channel set. Step 1326 includes routing, alonga second optical signal path in a second signal plane parallel to andoffset from the first signal plane, a second multiplexed signal from asecond common port to a second channel set. Substep 1328 includespropagating, from a second common port, the second multiplexed signalcomprising a first demultiplexed signal and a second demultiplexedsignal. Substep 1330 includes reflecting the first demultiplexed signalof the second multiplexed signal off the at least one first routingsurface having the first passband to a first channel port of a secondchannel set. Substep 1332 includes passing the second demultiplexedsignal of the second multiplexed signal through the at least one firstrouting surface. Substep 1334 includes reflecting, off the at least onesecond routing surface, the second demultiplexed signal of the secondmultiplexed signal passed through the at least one first routingsurface. Substep 1336 includes passing the second demultiplexed signalof the second multiplexed signal reflected from the at least one secondrouting surface through the at least one first routing surface to asecond channel port of the second channel set.

In certain embodiments, the at least one second routing surfacecomprises a second passband. In certain embodiments, the at least onesecond routing surface comprises a mirror. In certain embodiments, theat least one first routing surface comprises a single continuous firstrouting surface, and the at least one second routing surface comprises asingle continuous second routing surface.

In certain embodiments, the method further includes passing a thirddemultiplexed signal of the first multiplexed signal through the atleast one first routing surface. The method further includes passing thethird demultiplexed signal through the at least one second routingsurface. The method further includes reflecting, off at least one thirdrouting surface, the third demultiplexed signal that was passed throughthe at least one first routing surface and the at least one secondrouting surface. The method further includes passing the thirddemultiplexed signal reflected from the at least one third routingsurface through the at least one second routing surface and the at leastone first routing surface to a third channel port of the first channelset.

As similarly noted above, this method may be used with any number ofcommon ports and/or any number of channels.

Example Micro-Optical Devices and Components

FIG. 14 is a top view of a micro-optical device 1400 that could be usedwith any of the above embodiments. In general, the micro-optical device1400 includes at least one micro-collimator 1402 (e.g.,micro-collimators 1402P and 1402(1)-1402(4)) supported on an uppersurface 1404 of a support substrate 1406. In an example, themicro-optical device 1400 can include a housing 1408 that defines a WDMmodule. In an example, the WDM module can have a small form factor asdefined by length (e.g., in the range of 30 mm to 41 mm), width (e.g.,in the range of 14 mm to 28 mm), and height (within the range of 5 mm to6 mm).

The particular example of micro-optical device 1400 (may also bereferred to as a WDM micro-optical device 1400) is in the form of afour-channel WDM device that employs five of the micro-collimators 1402,including common micro-collimator 1402P and channel micro-collimators1402(1)-1402(4)), in optical communication with each other along anoptical signal path 1410 via WDM filters 1412(1)-1412(4). It is notedthat a more basic WDM micro-optical device 1400 can employ only threemicro-collimators 1402 and is used to separate or combine twowavelengths. Likewise, more complicated WDM micro-optical devices 1400can employ many more micro-collimators 1402 to separate or combine manymore wavelengths besides two wavelengths or even four wavelengths (e.g.,tens or even hundreds of different wavelengths). In examples, the WDMchannels can be dense WDM (DWDM) channels or coarse WDM (CWDM) channels.Other types of micro-optical devices 1400 besides the WDM micro-opticaldevice described herein can also be formed using the basic techniquesdescribed herein. For example, the micro-optical device 1400 can be usedto form many types of free-space optical fiber devices, as well ascompact variable optical attenuators, switches, optical amplifiers,taps, optical couplers/splitters, optical circulators, opticalisolators, optical time-domain reflectometer (OTDRs), etc.

In an example, the support substrate 1406 is made of glass (e.g.,quartz) or sapphire. In another example, the support substrate 1406 ismade of a glass that is receptive to the formation of glass bumps. Inother examples, the support substrate 1406 can be made of stainlesssteel or silicon, a low-CTE metal alloy (e.g., having a CTE of <10 ppm/°C., or more preferably CTE <5 ppm/° C., or even more preferably CTE <1ppm/° C.). Examples of metal alloys having such a low CTE include thenickel-iron alloy 64FeNi also known in the art under the registeredtrademarked INVAR® alloy or the nickel-cobalt ferrous alloy known in theart under the registered trademark KOVAR® alloy. In an example, theupper surface 1404 is precision polished to be flat to within atolerance of 0.005 mm so that the micro-collimators 1402 can beprecision mounted to the upper surface 1404. In an example, the supportsubstrate 1406 includes one or more reference features, such asalignment fiducials, for positioning and/or aligning themicro-collimators 1402 and other optical components (e.g., opticalfilters, other micro-collimators, etc.).

FIGS. 15-19 are views of example collimators and collimator arrays foruse with the components and devices of FIGS. 2A-12 and 14.

FIG. 15 is a perspective view of an example steel-tube collimator 1500for use with the components and devices of FIGS. 2A-12 and 14. Thesteel-tube collimator 1500 narrows a beam of particles or waves. Inother words, the steel-tube collimator 1500 causes the directions ofmotion to become more aligned in a specific direction. The steel-tubecollimator 1500 includes a steel-tube body 1502, with a curved lens 1504at one end of the steel-tube body, and a fiber optic pigtail 1506 at anopposite end of the steel-tube body.

FIGS. 16A and 16B are views of an example square tube collimator for usewith the components and devices of FIGS. 2A-12 and 14. The square tubecollimator 1600 includes a glass tube 1602 (e.g., cylindrical) with acentral bore 1604. As used herein, the term “cylindrical” is used in itsmost general sense and can be defined as a three-dimensional objectformed by taking a two-dimensional object and projecting it in adirection perpendicular to its surface. Thus, a cylinder, as the term isused herein, is not limited to having a circular cross-sectional shapebut can have any cross-sectional shape, such as the squarecross-sectional shape described below by way of example.

The square tube collimator 1600 further includes optical elements, suchas a collimating lens 1606, a ferrule 1608, etc., which can be securedto the glass tube 1602 using a securing mechanism (e.g., an adhesive).The collimating lens 1606 has a front surface 1610A and a back surface1610B opposite thereto. In the example shown, the front surface 1610A isconvex while the back surface 1610B can be angled, e.g., in the x-zplane as shown. In an example, the front surface 1610A of thecollimating lens 1606 can reside outside of the central bore 1604, i.e.,the front-end portion of the collimating lens 1606 can extend slightlypast the front end of the glass tube 1602. In an example, thecollimating lens 1606 can be formed as a gradient-index (GRIN) elementthat has a planar front surface 1610A. In an example, the collimatinglens 1606 can consist of a single lens element, while in another exampleit can consist of multiple lens elements. In the discussion below, thecollimating lens 1606 is shown as a single lens element for ease ofillustration and discussion.

The optical fiber support member is in the form of the ferrule 1608. Theferrule 1608 includes a central bore 1612 that runs between a front endand a back end along a ferrule central axis AF, which in an example isco-axial with the tube central axis AT of the glass tube 1602 and theoptical axis OA as defined by the collimating lens 1606. The centralbore 1612 can include a flared portion 1614 at the back end of theferrule 1608.

An optical fiber 1616 has a coated portion 1618, and a bare glass endportion 1620 which is bare glass (e.g., is stripped of the coatedportion) and is thus referred to as the “bare glass portion.” The bareglass end portion 1620 includes a polished end face 1622 that defines aproximal end of the optical fiber. The bare glass end portion 1620 ofthe optical fiber 1616 extends into the central bore 1612 of the ferrule1608 at the back end of the ferrule 1608. A securing element 1624 can bedisposed around the optical fiber 1616 at the back end of the ferrule1608 to secure the optical fiber to the ferrule 1608. The front end ofthe ferrule 1608 is angled in the x-z plane and is axially spaced apartfrom the angled back end of the collimating lens to define a gap 1626that has a corresponding axial gap distance DG. While a glass opticalfiber is described above, other types of optical fibers may be used,such as, for example, a plastic optical fiber.

The ferrule 1608, optical fiber 1616, and securing element 1624constitute a fiber optic pigtail 1628, which can be said to reside atleast partially within the bore 1604 adjacent the back end of the glasstube 1602. Thus, in an example, the square tube collimator 1600 includesonly the glass tube 1602, the collimating lens 1606, and the fiber opticpigtail 1628. The glass tube 1602 serves in one capacity as a small lensbarrel that supports and protects the collimating lens 1606 and thefiber optic pigtail 1628, particularly the bare glass end portion 1620and its polished end face 1622. The glass tube 1602 also serves inanother capacity as a mounting member that allows for the square tubecollimator 1600 to be mounted to a support substrate. In this capacity,at least one flat surface 1630 serves as a precision mounting surface.

In an example, the glass tube 1602, the collimating lens 1606, and theferrule 1608 are all made of a glass material, and further in anexample, are all made of the same glass material. Making the glass tube1602, the collimating lens 1606, and the ferrule 1608 out of a glassmaterial has the benefit that these components will very close if notidentical coefficients of thermal expansion (CTE). This feature isparticularly advantageous in environments that can experience largeswings in temperature.

In an example, the optical elements used in micro-optical systems aresized to be slightly smaller than the diameter of the bore 1604 (e.g.,by a few microns or tens of microns) so that the optical elements can beinserted into the bore 1604 and be movable within the bore 1604 to aselect location. In an example, the select location is an axial positionwhere the optical element resides for the micro-optical system to haveoptimum or substantially optimum optical performance. Here,substantially optimum performance means performance that may not beoptimum but that is within a performance or specification for themicro-optical system.

In another example, the optical elements have a clearance with respectto the bore 1604 in the range of a few microns (e.g., 2 microns or 3microns) to tens of microns (e.g., 20 microns up to 50 microns). Arelatively small value for the clearance allows for the optical elementsto be well-aligned with the central bore axis AB, e.g., to within a fewmicrons (e.g., from 2 microns to 5 microns).

The optical elements and the support/positioning elements can beinserted into and moved within the bore 1604 to their select locationsusing micro-positioning devices. The optical elements and thesupport/positioning elements can be secured within the bore 1604 using anumber of securing techniques. One example of a securing technique usesa securing feature that is an adhesive (e.g., a curable epoxy). Anothersecuring technique uses a securing feature that involves a glasssoldering to create one or more glass solder points. Another securingtechnique uses glass welding to create a securing feature in the form ofone or more glass welding points. A combination of these securingfeatures can also be employed.

Thus, one or more optical elements can be secured within the bore 1604using one or more securing features, and can also be supported and/orpositioned using one or more support/positioning elements. Thenon-adhesive securing techniques described below allow for themicro-optical systems disclosed herein to remain free of adhesives sothat, for example, micro-optical systems can consist of glass only.

FIG. 17A is a side view of an example compact collimator for use withthe components and devices of FIGS. 2A-14. A collimator 1700 includes alens 1702 (e.g., a glass or silica collimating lens), a fiber opticpigtail 1704, and a groove (e.g., a generally V-shaped groove) formed ina base 1706. The lens 1702 and the fiber optic pigtail 1704 are disposedin the groove. The lens 1702 is configured to receive a light signalprovided to the WDM multiplexer/demultiplexer from an external opticaltransmission system or provide a light signal multiplexed ordemultiplexed by the WDM to an external optical transmission system. Thelens 1702, for example, may be configured to receive a light signal froma fiber optic element for multiplexing or demultiplexing and/or toprovide a multiplexed or demultiplexed light signal to an external fiberoptic element. The fiber optic pigtail 1704 is optically coupled to thelens 1702 and is configured to provide a light signal to the lens 1702from the external fiber optic element and/or to receive the light signalfrom the lens 1702 for transmission to the external fiber optic element.

In various embodiments, the lens 1702 and the fiber optic pigtail 1704may or may not contact each other. The lens 1702 and the fiber opticpigtail 1704 may be securable to the groove independent of each other toallow for precise adjustment of a pointing angle between an optical beamfrom the collimator 1700 and a side and/or bottom surface of the groove.In addition, the lens 1702 and fiber optic pigtail 1704 may have thesame outer diameter.

The base 1706 of the collimator 1700 has a generally flat bottom surface1708 for mounting on a substrate of a WDM multiplexer/demultiplexer orother optical system. The base 1706 further includes a width that isless than a width of the lens 1702 and a width of the fiber opticpigtail 1704.

FIG. 17B is a close-up side view of the compact collimator of FIG. 17A.A pointing angle between an optical beam from the collimator 1700 andthe side and bottom surface of the groove can be eliminated (or at leastreduced) by controlling the relative position between the lens 1702 andthe fiber optic pigtail 1704 (see FIG. 17A) of the collimator 1700. Byfine tuning the position of the fiber optic pigtail 1704 to make anoutgoing beam come across a focal point of the lens 1702, a collimatedzero pointing angled beam with negligible off axis offset can beachieved. In one embodiment, for example, the tuning can be monitored bynear field and far field beam position comparison (e.g., using abeamscanner). The zero pointing angle collimating components are easier toattach to the substrate with little inclination, and more reliablebonding is possible due to the uniform epoxy or bonding agent. It isnoted that FIG. 17B is a schematic illustration used to illustrateconcepts of the description and that the ends of the glass lens and thefiber optic pigtail 1704 may be oriented at other angles, includingperpendicular, to the body of the glass lens and the fiber opticpigtail, respectively.

The structures of the collimator 1700 allow for easier modularizationand remove redundant degrees of freedom versus designs in which acollimator is coupled and attached to the substrate via external wedgesor supports. Thus, the collimator 1700 may reduce the complexity andfurther increase the device efficiency and process reliability of theoverall multiplexer/demultiplexer design.

FIGS. 18A-18B are views of an example array 1800 of the collimators 1700of FIGS. 17A-17B. The collimators 1700 are arranged side-by-side on asurface of a substrate 1802, the substrate 1802 including a plurality ofgrooves 1804 (discussed above). The grooves 1804 could be v-grooves orany other type of groove. A spacing between the substrate 1802 of theside-by-side collimators 1700 is greater than a spacing between thelenses 1702 (see FIGS. 17A-17B) and fiber optic pigtails 1704 (see FIGS.17A-17B) of the side-by-side collimators 1700.

FIG. 19 is a perspective view of an example of a fiber array unit (FAU)1900 and multi-lens array (MLA) 1902 for use with the components anddevices of FIGS. 2A-12 and 14. More specifically, the FAU 1900 includesa plurality of fibers 1904, and the MLA 1902 includes a plurality oflenses 1906. The FAU 1900 and MLA 1902 can be used with any of theembodiments discussed above.

FIG. 20 is a perspective view of a WDM device 2000 including the WDMassembly of FIGS. 7-12. The WDM device 2000 includes a com port assembly2002, a WDM assembly 2004, micro lens array (MLA) 2006, and a PIC(peripheral interface controller) interface 2008 (e.g., 32 channel PICinterface) with a grating coupler array (e.g., 4×8 grating couplerarray). In certain embodiments, the com port assembly 2002 includeseight com ports at a 250 μm pitch. The WDM assembly 2004 has a heightwithin 10-12 mm and is positioned over the grating coupler array of thePIC interface 2008. In certain embodiments, the WDM assembly 2004 can bepositioned directly on top of a copackaged optical chip (or any lasersignaling infrastructure). In certain embodiments, the WDM device 2000includes an orthogonal overlapped grating coupler instead of a gratingcoupler array. In certain embodiments, because the mux/demux is passive,the WDM assembly 2004 can be arranged elsewhere away from the copackagedoptical chip and connected to the optical chip by optical fibers. Incertain embodiments, the WDM device 2000 is a switch (e.g.,application-specific integrated circuit (ASIC) switch) and may be usedin an intra data center (e.g., east-west traffic).

It will be apparent to those skilled in the art that variousmodifications and variations can be made without departing from thespirit or scope of the invention.

Further, as used herein, it is intended that terms “fiber optic cables”and/or “optical fibers” include all types of single mode and multi-modelight waveguides, including one or more optical fibers that may beupcoated, colored, buffered, ribbonized and/or have other organizing orprotective structure in a cable such as one or more tubes, strengthmembers, jackets or the like. Likewise, other types of suitable opticalfibers include bend-insensitive optical fibers, or any other expedientof a medium for transmitting light signals. An example of abend-insensitive, or bend resistant, optical fiber is ClearCurve®Multimode fiber commercially available from Corning Incorporated.Suitable fibers of this type are disclosed, for example, in U.S. PatentApplication Publication Nos. 2008/0166094 and 2009/0169163.

Many modifications and other embodiments of the concepts in thisdisclosure will come to mind to one skilled in the art to which theembodiments pertain having the benefit of the teachings presented in theforegoing descriptions and the associated drawings. Therefore, it is tobe understood that the description and claims are not to be limited tothe specific embodiments disclosed and that modifications and otherembodiments are intended to be included within the scope of the appendedclaims. Although specific terms are employed herein, they are used in ageneric and descriptive sense only and not for purposes of limitation.

What is claimed is:
 1. A wavelength-division multiplexing (WDM)assembly, comprising: a first common port configured for opticalcommunication of a first multiplexed signal comprising a first signalcomponent and a second signal component; a first channel set including:a first channel port configured for optical communication of the firstsignal component of the first multiplexed signal; and a second channelport configured for optical communication of the second signal componentof the first multiplexed signal; a second common port configured foroptical communication of a second multiplexed signal comprising a firstsignal component and a second signal component; a second channel setincluding: a first channel port configured for optical communication ofthe first signal component of the second multiplexed signal; and asecond channel port configured for optical communication of the secondsignal component of the second multiplexed signal; at least one firstrouting surface having a first passband, the at least one first routingsurface being configured to: reflect the first signal component of thefirst multiplexed signal and the first signal component of the secondmultiplexed signal; and pass the second signal component of the firstmultiplexed signal and the second signal component of the secondmultiplexed signal; and at least one second routing surface configuredto reflect the second signal component of the first multiplexed signaland the second signal component of the second multiplexed signal backthrough the at least one first routing surface; wherein the first commonport, the at least one first routing surface, the at least one secondrouting surface, and the second channel port of the first channel setare configured to define a first optical signal path in a first signalplane; wherein the second common port, the at least one first routingsurface, the at least one second routing surface, and the second channelport of the second channel set are configured to define a second opticalsignal path in a second signal plane parallel to and offset from thefirst signal plane; wherein the at least one first routing surface ispositioned in the first optical signal path between the first commonport and the at least one second routing surface, and between the atleast one second routing surface and the second channel port of thefirst channel set; and wherein the at least one first routing surface ispositioned in the second optical signal path between the second commonport and the at least one second routing surface, and between the atleast one second routing surface and the second channel port of thesecond channel set.
 2. The WDM assembly of claim 1, wherein the at leastone second routing surface comprises a second passband.
 3. The WDMassembly of claim 1, wherein the at least one second routing surfacecomprises a mirror.
 4. The WDM assembly of claim 1, further comprising afirst WDM filter with a triangular cross-section, the first WDM filterincluding the at least one first routing surface, a first transmissivesurface, and a first reflective surface, wherein the first transmissivesurface is positioned in the first optical signal path between the firstcommon port and the at least one first routing surface, wherein thefirst reflective surface is positioned in the first optical signal pathbetween the first transmissive surface and the at least one firstrouting surface.
 5. The WDM assembly of claim 1, further comprising afirst WDM filter that includes the at least one first routing surfaceand a first transmissive surface opposite the at least one first routingsurface, wherein the first transmissive surface is positioned in thefirst optical signal path between the first common port and the at leastone first routing surface.
 6. The WDM assembly of claim 5, wherein theat least one second routing surface is positioned proximate to andoffset from the at least one first routing surface.
 7. The WDM assemblyof claim 6, further comprising at least one second WDM filter thatincludes the at least one second routing surface and a secondtransmissive surface opposite the at least one second routing surface,wherein the second transmissive surface is positioned proximate to theat least one first routing surface.
 8. The WDM assembly of claim 7,wherein: a first thickness of the first WDM filter between the firsttransmissive surface and the at least one first routing surface isgreater than a second thickness of the at least one second WDM filterbetween the second transmissive surface and the at least one secondrouting surface; and the second thickness of the at least one second WDMfilter is configured to define a pitch between signal paths of the firstsignal component of the first multiplexed signal and the second signalcomponent of the first multiplexed signal exiting the at least one firstrouting surface.
 9. The WDM assembly of claim 1, wherein the firstcommon port is aligned with the second common port in a common portplane perpendicular to the first signal plane and the second signalplane.
 10. The WDM assembly of claim 1, wherein the first channel portof the first channel set is aligned with the first channel port of thesecond channel set in a first channel plane perpendicular to the firstsignal plane and the second signal plane; and wherein the second channelport of the first channel set is aligned with the second channel port ofthe second channel set in a second channel plane perpendicular to thefirst signal plane and the second signal plane, the second channel planebeing parallel to and offset from the first channel plane.
 11. The WDMassembly of claim 1, further comprising a plurality of common portsarranged in a grid, each of the plurality of common ports configured todefine a respective optical signal path through the at least one firstrouting surface.
 12. The WDM assembly of claim 1, wherein the at leastone first routing surface comprises a single continuous first routingsurface, and the at least one second routing surface comprises a singlecontinuous second routing surface.
 13. The WDM assembly of claim 12,wherein: the first common port is configured for optical communicationof the first multiplexed signal comprising the first signal component,the second signal component, and a third signal component; the secondcommon port is configured for optical communication of the secondmultiplexed signal comprising the first signal component, the secondsignal component, and a third signal component; the WDM assembly furthercomprises a third channel port of the first channel set configured foroptical communication of the third signal component of the firstmultiplexed signal; the WDM assembly further comprises a third channelport of the second channel set configured for optical communication ofthe third signal component of the second multiplexed signal; the atleast one second routing surface is further configured to pass the thirdsignal component of the first multiplexed signal and the third signalcomponent of the second multiplexed signal; and the WDM assembly furthercomprises at least one third routing surface configured to reflect thethird signal component of the first multiplexed signal and the thirdsignal component of the second multiplexed signal back through the atleast one first routing surface.
 14. The WDM assembly of claim 1,further comprising a first WDM filter stack comprising a primary firstrouting surface of the at least one first routing surface and a primarysecond routing surface of the at least one second routing surface; andfurther comprising a second WDM filter stack comprising a secondaryfirst routing surface of the at least one first routing surface and asecondary second routing surface of the at least one second routingsurface; wherein the first WDM filter stack is positioned adjacent tothe second WDM filter stack.
 15. A wavelength-division multiplexing(WDM) assembly, comprising: a housing; a first common collimatorpositioned within the housing and configured for optical communicationof a first multiplexed signal, the first multiplexed signal comprising afirst signal component and a second signal component; a first commonfiber optic pigtail coupled to the first common collimator and extendingfrom the housing; a first channel set including: a first channelcollimator positioned within the housing and configured for opticalcommunication of the first signal component of the first multiplexedsignal, a first channel fiber optic pigtail operatively coupled to thefirst channel collimator of the first channel set and extending from thehousing; a second channel collimator positioned within the housing andconfigured for optical communication of the second signal component ofthe first multiplexed signal; and a second channel fiber optic pigtailoperatively coupled to the second channel collimator of the firstchannel set and extending from the housing; a second common collimatorpositioned within the housing and configured for optical communicationof a second multiplexed signal, the second multiplexed signal comprisinga first signal component and a second signal component; a second commonfiber optic pigtail coupled to the second common collimator andextending from the housing; a second channel set including: a firstchannel collimator positioned within the housing and configured foroptical communication of the first signal component of the secondmultiplexed signal, a first channel fiber optic pigtail operativelycoupled to the first channel collimator of the second channel set andextending from the housing; a second channel collimator positionedwithin the housing and configured for optical communication of thesecond signal component of the second multiplexed signal; and a secondchannel fiber optic pigtail operatively coupled to the second channelcollimator of the second channel set and extending from the housing; atleast one first routing surface having a first passband, the at leastone first routing surface being configured to: reflect the first signalcomponent of the first multiplexed signal and the first signal componentof the second multiplexed signal; and pass the second signal componentof the first multiplexed signal and the second signal component of thesecond multiplexed signal; and at least one second routing surfaceconfigured to reflect the second signal component of the firstmultiplexed signal and the second signal component of the secondmultiplexed signal back through the at least one first routing surface;wherein the first common collimator, the at least one first routingsurface, the at least one second routing surface, and the second channelcollimator of the first channel set are configured to define a firstoptical signal path in a first signal plane; wherein the second commoncollimator, the at least one first routing surface, the at least onesecond routing surface, and the second channel collimator of the secondchannel set are configured to define a second optical signal path in asecond signal plane parallel to and offset from the first signal plane;wherein the at least one first routing surface is positioned in thefirst optical signal path between the first common collimator and the atleast one second routing surface, and between the at least one secondrouting surface and the second channel collimator of the first channelset; and wherein the at least one first routing surface is positioned inthe second optical signal path between the second common collimator andthe at least one second routing surface, and between the at least onesecond routing surface and the second channel collimator of the secondchannel set.
 16. A method of using a wavelength-division multiplexing(WDM) assembly, comprising: routing, along a first optical signal pathin a first signal plane, a first multiplexed signal from a first commonport to a first channel set by: propagating, from a first common port,the first multiplexed signal comprising a first signal component and asecond signal component; reflecting the first signal component of thefirst multiplexed signal off at least one first routing surface having afirst passband to a first channel port of a first channel set; passingthe second signal component of the first multiplexed signal through theat least one first routing surface; reflecting, off at least one secondrouting surface, the second signal component of the first multiplexedsignal passed through the at least one first routing surface; andpassing the second signal component of the first multiplexed signalreflected from the at least one second routing surface through the atleast one first routing surface to a second channel port of the firstchannel set; and routing, along a second optical signal path in a secondsignal plane parallel to and offset from the first signal plane, asecond multiplexed signal from a second common port to a second channelset by: propagating, from a second common port, the second multiplexedsignal comprising a first signal component and a second signalcomponent; reflecting the first signal component of the secondmultiplexed signal off the at least one first routing surface having thefirst passband to a first channel port of a second channel set; passingthe second signal component of the second multiplexed signal through theat least one first routing surface; reflecting, off the at least onesecond routing surface, the second signal component of the secondmultiplexed signal passed through the at least one first routingsurface; and passing the second signal component of the secondmultiplexed signal reflected from the at least one second routingsurface through the at least one first routing surface to a secondchannel port of the second channel set.
 17. The method of claim 16,wherein the at least one second routing surface comprises a secondpassband.
 18. The method of claim 16, wherein the at least one secondrouting surface comprises a mirror.
 19. The method of claim 16, whereinthe at least one first routing surface comprises a single continuousfirst routing surface, and the at least one second routing surfacecomprises a single continuous second routing surface.
 20. The method ofclaim 16, further comprising: passing a third signal component of thefirst multiplexed signal through the at least one first routing surface;passing the third signal component through the at least one secondrouting surface; reflecting, off at least one third routing surface, thethird signal component that was passed through the at least one firstrouting surface and the at least one second routing surface; and passingthe third signal component reflected from the at least one third routingsurface through the at least one second routing surface and the at leastone first routing surface to a third channel port of the first channelset.